Stair Building; Porch Steps. Stair building is an art in itself and as such belongs to millwork rather than to carpentry. However, the carpenter must know the principles of simple stair lay-out and construction for he is called upon to construct porch steps, basement and often attic stairs. In smaller communities he may also have to build the main stair. Fig. 120 illustrates three common types of stair.
In planning a stair, the first requisite is to know its rise and run, Fig. 121. The rise in this case is the vertical distance measured
Types of Stairs from the top of the first floor to the top of the second floor. The run is the horizontal span of the stair.
A good average stair for a cottage will have a rise per step of 7 inches and a run of tread of 10 inches. Variations will have to be made in both rise and tread to meet conditions, but the student may take these dimensions as starting dimensions unless otherwise directed. Steps should not be either too steep, due to excessive rise per foot, or "slow" due to extreme width of step. An old rule for determining the relation of rise to tread is: "Twice the rise plus the tread should equal 24"."
Fig. 121. Rise and Run of Stair.
Proceed as follows: (1) Lay off on a story pole the total rise of the stair by placing the pole upright in the well hole. (2) Set a pair of dividers to 7" and step off this distance so marked. If there is a remainder, increase or diminish the divider's space and again step off the space. Continue this until a setting is obtained which gives no remainder. The number of risers will be found by counting the spaces, and the rise per step by measuring one of these spaces. (3) If the run of the stair is not of exact specification (some variation is usually possible) the run per step or tread may be determined by the rule just given. If a definite total run is specified the tread must be figured. (4) Since there is always one more riser than tread, the run per step is obtained by dividing the total run in inches by the number of risers less one. The numbers thus obtained for rise and run per step are the ones to be used on the framing square in laying out the stringers.
(5) Joint one edge of each stringer straight and square and place the framing square as in Fig. 122 and scribe along both blade and tongue. (6) Scribe the line A parallel to the 9" run, at a distance from it equal to the rise diminished by the thickness of the proposed tread. (7) Continue to lay the square as in (5) until the required number of steps have been laid out. A pitch board might have been constructed and made use of instead of the framing square in laying out the stringers. This is nothing more than a piece of stock which serves as a template by which to lay out the rise and run of each step, Fig. 123. A cleat or fence nailed to one edge after the three edges have been planed to dimensions permits easy and accurate placing of the same.
Fig. 122. Laying out String.
Fig. 123. Pitch Board..
Fig. 124. Economical Center Stringer.
(8) There remains the sawing out. On open stringers this is done by sawing square across the board or plank. Where the exposed ends of risers would make a bad appearance, the cuts in the stringers for risers are made mitering and the ends of the risers are mitered correspondingly. In either case the end of the riser will be flush with the exposed side of the stringer or string.
Fig. 124 illustrates an economical way of constructing a center stringer, a 2"x 4" having nailed to its top edge the waste cut from the side or wall stringers.